Natural gasoline conservation during in situ combustion



June 7, 19 66 H. w. PARKER 3,254,711

NATURAL GASOLINE CONSERVATION DURING IN SITU COMBUSTION Filed Aug. 29, 1963 NON-CONDENSIBLE GAS SEPARATOR X 28 i 36 NATURAL GAS WET NATURAL 54 42 GAS 56 L so 52 Is OVERBURDEN s I INJECTION WELL PRODUCTION WELL L L INVENTOR.

H. W. PARKER A TTOR/VEYS 3,254,711 Patented June 7, 1966 United States Patent Office 3,254,711 NATURAL GASOLINE CGNSERVATION DURING IN SITU COMBUSTION I Harry W. Parker, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Aug. 29, 1963, Ser. No. 305,404 6' Claims. (Cl. 166-7) usually oil, in the stratum adjacent an ignition well and propagating the front thru the stratum to one or more offset wells by either direct drive or inverse drive with a combustion-supporting gas. In a direct drive process, the combustion-supporting gas is injected thru the ignition well and the combustion front is propagated to one or more offset production wells from which the produced hydrocarbons and combustion gases are recovered as a vaporous efiluent. An inverse drive process comprises injecting the combustion-supporting gas thru one or more offset wells so that the said gas passes to the combustion zone and causes same to propagate toward the injection Well(s). In the inverse drive process, the ignition well functions as a production well.

It is conventional to inject a mixture of air and fuel gas as the combustion-supporting gas for propagating the combustion front. Such a process is disclosed in U.S. Patent 3,035,638 issued May 22, 1962, to H. W. Parker et al. The fuel gas is normally less than the stoichiometric concentration relative to the O in the injected air. This concentration is usually in the range of 1 to 5 percent by volume and more desirably in the range of 2 to 4 percent. Natural gas is the most practical fuel gas for mixing with the combustion air because of its low cost and ready availability in the average oil field. However, raw natural gas usually contains a substantial concentration of natural gasoline which is of considerably higher value as such than the value of the natural gas containing the same. In producing a carbonaceous stratum such as an oil sand, a tar sand, etc., by in situ combustion, whether as a primary, secondary or tertiary phase, considerable natural gas and natural gasoline are consumed.

This invention is concerned with the recovery of natural gasoline from raw natural gas which is being utilized as the fuel gas in an in situ combustion process.

Accordingly, an object of the invention is to provide a process and arrangement of apparatus for recovering natural gasoline from raw or wet natural gas being utilized as the fuel gas in an in situ combustion process for the recovery of hydrocarbons from a carbonaceous stratum. Another object is to reduce the over all cost of an in situ combustion process. A further object is to conserve valuable natural gasoline when utilizing raw natural gas as the injected fuel gas in in situ combustion operations. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises contacting wet or raw natural gas with liquid oil from a production well in an in situ combustion operation was to extract natural gasoline from the natural gas and recover same in the produced oil while passing the denuded natural gas to the injection well(s) as the fuel for supplementing the in situ combustion step of the process.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawas a tar sand 10 is penetrated by an injection well 12 and a production well 14. Other wells are usually involved in the pattern but are omitted for simplicity in describing the invention. Well 12 is provided with a casing 16 and an injection tubing 18 extending thru well head 20. A similar arrangement in well 14 comprises casing 22, production tubing 24, and well head 25. 7

An air supply line 26 and a natural gas injection line 28 connect with injection tubing 18. Eflluent line 30 from production tubing 24 leads into a condenser 32, the outlet line 34 of which leads into separator 36. This separator efl'ects separation of the condensed effluent so as to produce a water phase 37, an oil phase 38 and an uncondensed gas phase 39. A water withdrawal line 40, an oil withdrawal line 42, and a gas withdrawal line 44 connect with separator 36 for removal of the corresponding phases therefrom.

An adsorber 46 is provided with an inlet oil line 48, which connects with oil line 42, and an outlet line 50 for rich oil which leads into oil production line 52. Line 54 connects line 42 with line 52 for bypassing any portion of i the oil not required in adsorber 46. The adsorber is also provided with feed line 56 for raw natural gas and with efiiuent gas line 28 for passing lean natural gas into injection conduit 18. Line 58 connects with effluent line 28 for withdrawal of lean natural gas in excess of the requirements of the in situ combustion process.

At the stage of production illustrated in the drawing, a combustion front 60 is being propagated toward well 12 inversely to the flow of combustion supporting air and fuel gas introduced thru tubing 18 and forced thru the intervening stratum to combustion front 60. v This inverse drive process was initiated by igniting stratum 10 around Well 14 by methods well known in the art and feeding combustion supporting gas (air and fuel gas) into the stratum thru well 12 and thru the stratum to the igniting area. A direct drive process with the arrangement shown -would involve initiating the combustion front adjacent well 12 and propagate the front toward Well 14 by combustion-supporting gas injected thru tubing 18.

In either the direct or inverse drive process, the produced gases and vapors pass thu line 30 into condenser 32 which is cooled by any conventional means such as by circulation of water therethru in indirect heat exchange with the eflluent in line 30 so as to condense at least a substantial proportion of the oil vapors and the water produced and driven from the stratum. The condensate is passed thru line 34 into separator 36 for phase separation into a water phase 37, an oil phase 38, and a gas phase 39. The liquid oil is passed thru lines 42 and 48 into the upper end of adsorber 46 and into countercurrent con tact with raw or wet natural gas introduced thru line 56 into the bottom of vessel 46 in conventional manner whereby the oil adsorbs natural gasoline from the natural gas. The rich oil then passes thru line 50 into line 52 for transfer to storage or pipe line.

Natural gas. denuded of natural gasoline passes thru line 28 into tubing 18 in admixture with air from'line 26 and into the stratum to the combustion front 60 where the fuel gas is burned to supply a portion of the heat for sustaining the in situ combustion, leaving excess air for combusting in-place hydrocarbon material. The produced hydrocarbons and combustion gases together with any water produced from the stratum passes into the well 14 in vapor form and is' produced thru tubing 24.

It is feasible to feed natural gas in excess of the requirements of the in situ combustion process into adsorber 46 thru line 56 and Withdraw excess lean natural gas thru line 58 for delivery to storage and/ or market. Usually, the amount of oil passing thru line 42 is in excess of the amount needed for adsorption in vessel 46 and this excessive oil is passed thru line 54 into line 52 without passing thru adsorber 46. Thus, the oil produced by the in situ combustion is substantially enriched in gasoline boiling range hydrocarbons by the extraction process effected in vessel 46 and the resulting product is more valuable than would otherwise be the case. Only the less valuable natural gas constituents are burned in the combustion front to supplement the heat supplied by burning formation hydrocarbons.

Adsorber 46 may be any conventional type of adsorber in which an oil'is utilized for adsorbing lighter constituents from a gas stream. It is also feasible to fractionate the oil in line 42 to prepare a more suitable oil for adsorption in the adsorber.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. in a process for producing hydrocarbons from a subterranean oil-bearing stratum by in situ combustion comprising igniting said stratum adjacent a well therein to establish a combustion from; continuously feeding a mixture consisting essentially of air and wet natural gas to said front so as to burn said gas in said front along with in-place oil to propagate same toward another well in said stratum; and producing an efiiuent comprising gas and oil vapors thru one of said wells, the improvement comprising the steps of:

(1) condensing oil vapors from said efiiuent;

(2) passing the condensed oil thru an absorber in contact with said wet natural gas thereby extracting natural gasoline from said natural gas in said oil; and

(3) recovering the enriched oil.

2. A process comprising the steps of:

(1) producing hydrocarbons from a subterranean oilbearing stratum principally by in situ combustion including establishing a combustion front in said stratum, feeding a mixture consisting essentially of air and'less than the stoichiometric equivalent of fuel gas to said front so as to burn said fuel gas within said front along with stratum oil to propagate said front thru said stratum, and recovering an eflluent comprising said hydrocarbons;

(2) recovering a liquid oil fraction from said efiluent;

(3) contacting a raw natural gas from a source other than said step (1) with said oil fraction so as to extract natural gasoline from said gas; and

(4) utilizing natural gas from step (3) as said fuel gas.

3. The process of claim 2 wherein said combustion front is propagated by direct drive of said mixture.

4. The process of claim 2 wherein said combustion front is propagated by inverse drive of said mixture.

5. Apparatus comprising in combination:

(1) an injection conduit free of burner means in a first well penetrating an oil-bearing stratum;

(2) a production conduit in a second well penetrating a section of said stratum adjacent said first well;

(3) cooling and condensing means for oil and water;

(4) a conduit leading directly from the production conduit of (2) into the means of (3);

(5) separation means for separation of oil, water, and

uncondensed fluids having an inlet connected directly by conduit means with the means of (3) and separate outlets for water, oil, and uncondensed fluids;

(6) oil absorption means having an inlet for absorption oil in its upper end connected with the oil outlet of (5), an outlet for rich oil in its lower end, an inlet for wet natural gas in its lower end and an outlet in its upper section for lean natural gas;

(7) conduit means connecting the outlet for lean natural gas of (6) with the injection conduit of (1); and

(8) an air supply line connected with said injection conduit.

6. Apparatus comprising in combination:

(1) an injection conduit in a first well penetrating an oil-bearing stratum;

(2) a production conduit free of burner means in a second Well penetrating a section of said stratum adjacent said first well;

(3) first means connected directly with the conduit of (2) for recovering a liquid oil fraction from produced fluids in said production conduit having an efiluent line for said oil fraction;

(4) second means connected with the effiuent line of (3) for contacting raw natural gas with recovered oil of (3) and passing residual natural gas to said injection conduit; and

(5) means for feeding air along with residual natural gas into said injection conduit.

References Cited by the Examiner UNITED STATES PATENTS 2,355,167 8/1944 Keith 1668 X 2,423,156 7/1947 Reid 166-7 X 2,642,943 6/1953 Smith et a1. 166--11 2,718,263 9/1955 Hellman et a1 166-11 2,813,583 11/1957 Marix et al. 16611 3,035,638 5/1962 Parker et a l. 1661l CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner.

S. J. NOVOSAD, Assistant Examiner. 

2. A PROCESS COMPRISING THE STEPS OF: (1) PRODUCING HYDROCARBONS FROM A SUBTERRANEAN OILBEARING STRATUM PRINCIPALLY BY IN SITU COMBUSTION INCLUDING ESTABLISHING A COMBUSTION FRONT IN SAID STRATUM, FEEDING A MIXTURE CONSISTING ESSENTIALLY OF AIR AND LESS THAN THE STOICHIOMETRIC EQUIVALENT OF FUEL GAS TO SAID FRONT SO AS TO BURN SAID FUEL GAS WITHIN SAID FRONT ALONG WITH STRATUM OIL TO PROPAGATE SAID FRONT THRU SAID STRATUM, AND RECOVERING AN EFFLUENT COMPRISING SAID HYDROCARBONS; (2) RECOVERING A LIQUID OIL FRACTION FROM SAID EFFLUENT; (3) CONTACTING A RAW NATURAL GAS FROM A SOURCE OTHER THAN SAID STEP (1) WITH SAID OIL FRACTION SO AS TO EXTRACT NATURAL GASOLINE FROM SAID GAS; AND (4) UTILIZING NATURAL TAS FROM STEP (3) AS SAID FUEL GAS.
 6. APPARATUS COMPRISING IN COMBINATION: (1) AN INJECTION CONDUIT IN A FIRST WELL PENETRATING AN OIL-BEARING STRATUM; (2) A PRODUCTION CONDUIT FREE OF BURNER MEANS IN A SECOND WELL PENETRATING A SECTION OF SAID STRATUM ADJACENT SAID FIRST WELL; (3) FIRST MEANS CONNECTED DIRECTLY WITH THE CONDUIT OF (2) FOR RECOVERING A LIQUID OIL FRACTION FROM PRODUCED FLUIDS IN SAID PRODUCTION CONDUIT HAVING AN EFFLUENT LINE FOR SAID OIL FRACTION; (4) SECOND MEANS CONNECTED WITH THE EFFLUENT LINE OF (3) FOR CONTACTING RAW NATURAL GAS WITH RECOVERED OIL OF (3) AND PASSING RESIDUAL NATURAL GAS TO SAID INJECTION CONDUIT; AND (5) MEANS FOR FEEDING AIR ALONG WITH RESIDUAL NATURAL GAS INTO SAID INJECTION CONDUIT. 